The proposed research is intended to address the problem of extravasation events in the neonatal and pediatric patient population. Extravasations of intravenous fluids in children can have serious consequences when gross extravasations occur. Skin necrosis can occur which may require treatment with skin grafting These adverse sequelae are infrequently in the adult patient, but in newborns and young children they are much more prevalent and can be catastrophic. The proposed research is intended to evaluate newly available Passive Microwave Radiometry (PMR) technology as a modality for early detection of extravasation events in children. The PMR technique is passive, non-invasive and measures subcutaneous tissue temperatures. Emphasis will be placed on optimizing the transducer(antenna) element for the injection site anatomy and tissue characteristics normally encountered for the neonatal and pediatric patient. In-vivo experiments, using an appropriate animal model, will be used to evaluate the ability of the system to distinguish between normal IV infusions and extravasated infusions. The performance data collected in the proposed program will be used to develop the transducer into a sterile, disposable element in the follow-on Phase II effort. In addition data collected to distinguish between normal and extravasated infusions will used to implement an embedded microcontroller based monitor.